[LeArc] Forecast Discussion : MLI@ 4/4/2003 5:40:24 PM

[learc@mailman.qth.net]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 042337
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
537 PM CST FRI APR 4 2003

LATE DISCUSSION TODAY.  WILL FOCUS ON POTENTIAL FOR LATE-SEASON SNOW
EVENT SUNDAY...SUNDAY NIGHT...AND MONDAY MORNING.

SURFACE LOW LATE THIS AFTERNOON IS NEAR EOK...ALONG A SOUTHWEST
MISSOURI TO NORTH CENTRAL ILLINOIS COLD FRONT...WITH A SECONDARY LOW
BACK INTO SOUTHWEST MISSOURI. THE 500MB TROUGH IS STILL BACK OVER
WESTERN IOWA.  ALL OF THIS IS PRETTY MUCH IN LINE WITH WHAT THE AVN
HAD BEEN ADVERTISING THE LAST FEW RUNS...WITH SLOWER PROGRESS
ACROSS THE AREA TODAY.  SEVERE THUNDERSTORMS...HAILERS...HAVE MOVED
WELL EAST OF THE AREA. HAD THUNDER-SNOW LATE THIS AFTERNOON NORTH...
BUT THAT IS ALSO SHIFTING NORTH AND EAST.

THE PRIMARY FORECAST CONCERN OVER THE NEXT 7 DAYS IS SUNDAY
AFTERNOON THRU SUNDAY NIGHT AND INTO MONDAY MORNING...WITH A
SURFACE LOW MOVING EAST ALONG THE MISSOURI-ARKANSAS LINE SUNDAY NIGHT
AND A CLOSED 500MB LOW MOVING OVER THE FORECAST AREA MONDAY MORNING
AND MIDDAY. THE SHORT- AND MEDIUM-RANGE MODELS ARE IN GENERAL
AGREEMENT ON THESE FEATURES...WITH PRECIP BEGINNING SUNDAY
AFTERNOON.  PRECIP WILL BE RAIN AT ONSET...BUT WILL SWITCH QUICKLY
OVER TO SNOW FROM ROUTE 30 NORTH...AND WITHIN A RELATIVELY SHORT
PERIOD ALONG THE INTERSTATE 80 CORRIDOR.  FURTHER SOUTH TO BRL AND
EOK...PRECIP WILL BE ALL RAIN...CHANGING TO SNOW IN THE EVENING.
CHANGE-OVER COULD BE AS LATE AS 06Z IN MACOMB.  MODEL QPF IS STILL
IN DISAGREEMENT...BUT IT LOOKS LIKE A GOOD CHANCE OF AROUND A HALF
INCH OF LIQUID EQUIVALENT ACROSS THE AREA.  DRAWBACKS WILL BE THE
RELATIVELY WARM GROUND...INITIAL LOSE TO LIQUID AT ONSET...AND RATIOS
OF 10 TO 1 OR LESS. HOWEVER...4 TO 8 INCHES OF SNOW SEEMS LIKE A GOOD
POSSIBILITY ACROSS AT LEAST A PORTION OF THE FORECAST AREA...WITH THE
BEST CHANCE FOR SIGNIFICANT ACCUMULATION CURRENTLY BEING NEAR THE I-
80 CORRIDOR. CONFIDENCE IS NOT HIGH ENOUGH AT THIS TIME FOR A WATCH
...DUE TO THE POSSIBILITY OF THE PRIMARY DEFORMATION SNOW FALLING
JUST NORTH OF THE AREA...AND THE SNOW/RAIN PRECIPITATION ASSOCIATED
WITH LOWER LEVEL FORCING BEING SOUTH OF THE FORECAST AREA.  ONE VERY
FAVORABLE PARAMETER IN THE 12Z AVN AND ETA MODEL RUNS IS THE TRACK OF
THE VORT MAX ACROSS THE SOUTHERN PORTION OF THE FORECAST AREA.  THIS
WOULD PUT THE BEST POTENTIAL FOR SIGNIFICANT SNOW...TO THE LEFT OF
THE VORT TRACK...ALONG THE I-80 CORRIDOR.  THE UPDATED HWO WILL
REFLECT CURRENT THINKING. IF MODELS STILL ON TRACK FOR 00Z RUN...WILL
NEED A WATCH.

LITTLE CHANGE TO THE ONGOING FORECAST.  HAVE EMPHASIZED THE LATE
WEEKEND SNOW EVENT.  THE POSSIBILITY OF MEASURABLE SNOW CONTINUING ON
INTO MONDAY WILL BE SOMETHING TO CONSIDER IN LATER PACKAGES.

.DVN...
IA...NONE.
IL...NONE.
MO...NONE.

$$

REA